The invention is based on a device for measuring the mass of a flowing medium as set forth hereinafter. A device is already known (German Patent 30 07 851), in which to measure the mass or flow rate of a flowing medium, a temperature-dependent sensor element in the form of a hot wire is introduced into the flowing medium. The sensor element is connected by means of sensor connection lines to an electrical control circuit, which evaluates the electrical signals furnished by the sensor element. The device has a metal housing which serves to accommodate and retain the control circuit and the sensor element. The control circuit is accommodated in the interior of the housing, protect the electronic control circuit particularly against entering electromagnetic waves. Such a provision for protection of electronic circuits is known to one skilled in the art as electromagnetic compatability protection (EMC protection), which is gaining increasing significance especially in motor vehicles, since motor vehicles are increasingly being equipped with electronic or electric devices. These devices are accommodated particularly in the interior of the engine, close to one another, and must therefore function side by side without affecting one another, so that not only must they be protected against electromagnetic waves entering from outside, but the mutual influence of the devices on one another must also be precluded. The metal housing shown in the prior art cited requires considerable space, however, and the connection lines are extended to the control circuit from outside the metal housing. The connection lines are necessary in order on the one hand to pick up the electrical signals furnished by the control circuit and on the other to connect the control circuit to a voltage source. However, the connection lines are carried to the control circuit from the outside to the interior of the metal housing without distortion suppression, so that electromagnetic waves in the form of interference pulses can reach the control circuit over the connecting lines and impair its function or in the worst case destroy it.
German Patent 28 45 661 shows a device for measuring the mass or flow rate of a flowing medium, especially of the air aspirated by an internal combustion engine, in which electrical signals of a sensor element are evaluated by an electronic control circuit which has a number of electrical components, which are combined in so-called hybrid fashion to make a hybrid circuit. The hybrid circuit is applied to a hybrid substrate as an integrated film circuit and glued with an adhesive to a basic housing of plastic, without there being any metal housing for EMC protection of the control circuit.